Powertrains having an internal combustion engine coupled to a continuously or infinitely variable transmission (CVT) may be employed to provide tractive effort in vehicles. A CVT is capable of continuously changing an input/output speed ratio over a range between a minimum (underdrive) ratio and a maximum (overdrive) ratio, thus permitting infinitely variable selection of engine operation that achieves a preferred balance of fuel consumption and engine performance in response to an operator torque request.
Known chain-type continuously variable transmissions include two pulleys, each having two sheaves. A chain runs between the two pulleys, with the two sheaves of each of the pulleys sandwiching the chain therebetween. Frictional engagement between the sheaves of each pulley and the chain couples the chain to each of the pulleys to transfer torque from one pulley to the other. One of the pulleys may operate as a drive or input pulley, and the other pulley may operate as a driven or output pulley. The gear ratio is the ratio of the torque of the driven pulley to the torque of the drive pulley. The gear ratio may be changed by urging the two sheaves of one of the pulleys closer together and urging the two sheaves of the other pulley farther apart from each other, causing the chain to ride higher or lower on the respective pulley.
Known toroidal continuously variable transmissions include discs and roller mechanisms that transmit power between the discs. The toroidal continuously variable transmission includes at least one input disc, connected to the engine, and one output disc operatively connected to the transmission output. The input disc and output disc define a cavity therebetween. The cavity defines a toroidal surface. The roller mechanism is placed within the cavity and is configured to vary the torque transmission ratio as the roller mechanism moves across the toroidal surface.